Private-branch intercommunicating telephone system.



J. L. MOQUARRIE. PRIVATE BRANCH INTERCOMMUNIOATING TELEPHONE SYSTEM.

APPLICATION FILED NOV. 23, 1907.

969,799. Patented Sept. 13,1910.

STATION N 1 1710mm N 1.

TRUNK N 2 7. STATION N 3,

UNITED STATES PA TENT OFFICE.

JAMES L. MGQUARRIE, OF OAK PARK, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

PRIVATE-BRANCH INTERCOMMUNICATING TELEPHONE SYSTEM.

Specification of Letters Patent. Patented Sept. 13, 1910.

Application filed November 23, 1907. Serial No. 403,510.

exchange telephone system, embodying an intercommunicating system, and also providing for outside connections with the central ofiice exchange. Its object is to provide an arrangement whereby local communication may be had between the parties at the several stations in the private exchange without the intervention of an operator, and whereby the telephone used for answering an outside call may be utilized for communicating with another local station without causing a disconnect signal at the central oflice during the interval of such use.

A further object is to provide for secret communication between the station of the intercommunicating system at which the call over the trunk line is received and any other local station, without the central oflice operator hearing the conversation.

My invention consists in the provision of means at two or more stations of an intercommunicating system for maintaining the circuit continuity of a line leading to said system from the central oflice exchange, said means being in addition to and in substitution of the telephone set at said stations.

My invention thus provides means for holding a'calling line while the telephone set which was used in answering the call is being utilized for communicating with another local station.

My invention further provides means whereby said call may be transferred to another station without the act of transferring establishing conditions at the central oflice causing the display of a disconnect signal. Y

My invention also provides means for holding a trunk line while the station at.

which the call is received has communication with another local station, without the central oflice operator hearing the connection.

In the preferred embodiment of my invention, the trunk line from the central ofiice terminates in an intercommunicating system and is multipled with the several stations of such-system. Means are pro vided at each station for connecting that station with the trunk line, and a circuit closing device is also located at each station for completing the circuit continuity of said trunk line irrespective of the telephone set, thus permitting the disconnection of the telephone set from the trunk line without afiecting the central oiiice si nals. Communication may then be had rom that station to another over their local lines, without the central office operator hearing the conversation, while said circuit closin device is maintaining the continuity o the trunk line to prevent the display of the disconnect signal to the central ofiice.

My invention may be more readily understood by reference to the accompanyin drawing, which is a diagram of circuits and apparatus which may be employed.

For sake of clearness, only two stations of the intercommunieating system and two trunk lines terminating therein are shown, it being obvious that as many trunk lines may be employed as may be-deemed necessary and that the stations of the system may be duplicated within the usual limits.

Considering first merely the intercommunicating feature of the system illustrated in the drawing, each station, as shown for example at station No. I and station No. 2, is equipped with the usual telephone set comprising a transmitter t and a receiver 1'. Correspondin with each station is a local line 1, 1 an 2, 2, respectively, connected with a common battery B through the usual retardation coils C. Each station is pro-' vided with local keys associated with the local lines of every other station, those at line selected y the operatlon of the local key. At each station is the usual call bell b, the circuit through which is closed at the switch contacts when the receiver is on its hook. The battery B furnishes the source 7 one key releases any key already locked down. The manipulation of key R, however, has no effect on any other key.

The manner in which a subscriber at one station may call up-another station is obvious. For example, if the subscriber at station No. 1 desires to communicate with station No. 2, he will remove his receiver 1- from its switch hook it, and depress keyL thus closing contacts 8, 4 and connecting his telephone set with local line 2, 2*. He will then depress his ringing key R, thereby closing contacts 5 and .6, whereupon, if the called line is not in use, current will fiow from battery B through conductor 7, contact 5, resistance 8, conductor 9, contact 3 of key L conductors 10, 2, 11, 12, bell Z), contact 13, conductor 14, back to battery B. The subscriber at station No. 2 will respond by depressing his answering key A and by removing his receiver 1' from its hook. Stations 1 and 2 are now in tele-. phonic communication, their telephone sets being connected to local line'2, 2, through local key L and answering key A, respectively. t The circuit arrangement just described provides means whereby the calling party is informed whether or not the station called is busy. At the time the party at station No. 1 depressed his ringing key R, current was supplied for ringin the bell b at station N o. 2, said current owing through resistance 8. The terminals of the receiver 1' are connected through conductors 9,16 to each side of said resistance. The ringing of the bell b at station No. 2 causes a buzz in the receiver 1', due to the difference in potential across the terminals of resistance 8, this resistance being in series with the bell at station No. 2. The current flowing through resistance 8 is intermittent, owing to the opening and closing of the circuit in the usual manner in the contact of the bell b. The buzz denotes to the party at sta tion No. 1 that the telephone at station No. 2 is not in use, since if it were, contact 13 would be open, the bell b at station No. 2 would not ring, and consequently the party at station No. 1 would not hear a buzz 1n his receiver. t

It will be observed thatthe arrangement thus far described in detail provides what. is commonly designated as an intercommunieating system.- I will now describe the circuits and arrangement whereby such: a sys tem may be connected to a central oflice exchange to provide for outside communication, and means permitting transferring of lines No. 1 and No. 2, respectively, extending from the central otfice exchange to the intercommunicating system. Each trunk is multipled, as shown, with each station of the intercommunicating system. Each station is provided with trunk keys T, T associated with trunk No. 1 and trunk No; 2, respectively, and adapted when depressed to connect the telephone set of that station with the corresponding trunk 1ine'.a Each station is also provided with a transfer key associated with each trunk line, those for trunk lines No. 1 and No. 2, being indicated at K and K respectively. The function of said keys is to maintain the continuity of the signaling circuit established over the trunk line in substitution of the'telephone set, thus enabling that station to call u and communicate with any other station without giving a disconnect signal at the central ofiice. Said transfer keys are held down when depressed by means of a plate E, and

ized at the time the receiver at that'station is returned to its hook, providing a transfer key had been previously depressed. By pressing down transfer key K or K a bridge is placed across the corresponding trunk line. Such bridge preferably includes P a resistance R and acts as. a holding coil in substitution of the telephone set for preventing a disconnect signal from being dis-. played at the central ofiice.

Signal bells s, and 3 may be associated with the trunk lines in any manner to give a signal at the station or stations at which it is desired to answer an incoming call. These bells may be located at some point, for example, where they can be heard from any station.

It is apparent that a call over any one of the trunk lines may be answered at any station, and the answerin station may thereafter secretly communlcate with any other station without giving a disconnect signal at the central ofiice. Furthermore, the answering station may then either renewthe conversation with the calling party, or

Current then flows 'are released by a magnet F which is ener switch hook h, transmitt r t, conductor 24,

contact 25 of key T, con uctor 26 and con ductor 18 of the trunkline to central oflice.

. in which is included the telephone receiver,

has been'est blished, which path is local to the private ii ary to the main line circ 't. Such path may be traced as follows: rom conductor 18,

through condenser G, winding 27 of induction coil H, conductors 28, 29, contact 30 of tinuity of the signaling circuit 0 key T, conductor 9, receiver 1", switch hook it, transmitter 15, conductor .24, contact 25 of key T, conductors 26 and 18 back to the point where condenser G connects to conductor 18. StationNo; 1 is now so connectedto trunk line No. 1 that conversation can take place between the private branch exchange party and the" calling party, connected through the central exchange, the party at statlon No. 1 controlling the central ofiice signals in the usual manner, that is, by-means of his switch. hook. If the party at station No. 1 now wishes to call up any other station of the intercommunieating system for any purpose, as for example to receive instructions, or to transfer the call, he presses down the transfer key K, which key is then held down by the plate E. The closing of contact 31 of the key K places a bridge across the trunk line conductors 17, 18, thus maintainin the conthat line, and leaving the party at station No. 1 at liberty to use his tele hone for calling up any other station of t e private branch exchan e. For example, he may call up station' 0. 2 in the manner hereinbefore de- T e party at station No. 1,after requesting l scribed. In so doing, he depresses local key L thereby releasing trunkey T and completely disconnecting his telephone set from the trunk line, but leavin as before stated, the bridge closed by key in substitution thereof. By again pressing down trunk keyT, he may at any time resume his conversation with the outside calling party. atv station No. 1 desires to transfer the call to Let us assume, however,' that the party station No. 2. After pressing down transfer key K and calling up station No. 2 in the usual manner, he instructs the party'at that station to answer over trunk line No. 1. The party,at station No. 2 then depresses his trunk key? T and in so doing releases his answerin key, leavin his telephone set connects only with t e trunk line. The party at station No. 2 is nowin position to talk with the outside calling party. The

circuits established through the connections of station N o. 2 are substantially the same as those hereinbefore, traced from the trunk line through station No. 1 and may be readil followed without further description.

ranch exchange and is seconda the party at station No. 2 to answer over trunk No. 1, replaces his receiver on its hook, thereby causing the automatic release of his transfer key K", which is effected b the electromagnet F becoming momentari y energized and attracting the plate E, moving it so as to release said key. Said ma net is energized by current flowing from attery B contact 33 of ey K, winding of magnet F, contact 34 closed by the switch hook, and conductor 35 back to battery B. As soon as the ke K is released, the contact 33 in the circuit just traced is opened and current ceases to flow in said circuit. As before stated, the bridge of the trunk line closed by the transfer key preferably includes a resistance R; for otherwise such bridge would practically short-circuit the telephone set at station No. 2 and prevent conversation between that station and the central station operator until after the part at station No. 1 had hung .up his receiver. en the party at station No. 2 hangs up the receiver at the end of the conversation, the contacts which had been closed by the switch hook are opened, thereby giving the usual disconnect si al to the central ofiice operator.

It w1ll be noted. that the arrangement of the keys at each station is as follows: The ringing key B does not lock down nor does its operation release any other keys. The remaining keys associated with the plate ,D release each other, and a ke when depressed locks in that position. T e transfer keys throu h conductor 7, conductor 32,.

K K release-each other and the depressed key'remains locked down. The magnet F attracts the plate E and releases any transfer key that may be down at the time the flele hone at that station is restored to its It will be observed that substantiall the same conditions ap 1y whether a, cal received over the trun line is actually transferred from the station answering the call to another one of the local stations or whether the answerin station, without losin connection with t e trunk line, merely tal s with another station, as for example, for the purpose of obtaining informat on. Hence it will be understood the terms transfer and transfer-key, in their broad sense, are applicable to bot-h of the above-mentioned conditions.

I claim 1. The combination with an intercommunicating telephone system, of a trunk line leading from a central office exchange to said intercommunicating' system and multipled with two or more stations thereof, and means at each of said stations, additional to and in substitution of the telephone setthereof, for maintaining the circuit continuity of said-trunk line.

2. The combination with an intercommw nicating telephone system, of a trunk line leading from a central ofiice exchange to said lntercommunicating system and multipled with two or more stat-ions thereof,

communicating system and multipled with two or more stations thereof, switching mechanism at said stations for placing the telephone set thereof into telephonic communication over said trunk line, additional means associated with said trunk hne for maintaining the circuit continuity of the trunk line, and switching means at each station for substituting said additional means for the telephone set too-maintain the central oflice signals unchanged.

4. The combination with an intercommunicating telephone system, of a trunk line I leading from a central office exchange to said inter-communicating system and multipled with two or more stations thereof, and

means at said stations for transferring a call over the trunk line, said. means including a circuit closing device individual to the trunk line for maintaining the circuit continuity of said trunk line during the intervals of the transfer.'

'5. The combination with an intercommunicating telephone system, of a trunk line leading from a central oflice exchange to said intercommunicating system and multipled with two or more stations thereof, and

a circuit closing device at said stations associated with said trunk line and adapted to be substituted for the telephone set of the station for maintaining the circuit continuity bf the trunk line.

6. In a telephone system, the combination with an intercommunicating system, of a line, and means for transferring a call from trunk line leading from an outside exchange and multipled with each station of the inter-' communicating system, means at said statlons for answering a call over sald trunk the answering station to any other of the stations, said means including means for maintaining the circuit continuity of the trunk line during the interval of transfer;

' 7. A telephone system, comprising a trunk line terminating in an intercommunicating. system and" multlpled with two or more stations thereof, means for connectingany of said stations with the trunk line, and a cirline associated with the cuit closing device located at each station and having connection with said trunk line, said circuit closing device when operated maintaining the continuity of said trunk line, thereby permitting the disconnection of the .telephonesetat that station from the trunk line andits use for communication from that station to another independent of said trunk line while holding the call over said trunk 8. The combination with an' intercommunicating telephone system, of a trunk line leading from a central oflice exchange to said intercommunicating system and multipled with two or more stations thereof, switching mechanism at said stations for connecting the telephone set at each station with the trunk line, means at each of said stations additional to andin substitution of the telephone set thereof, for closing the circuit of said trunk line.

9. In an intercommunicating telephone system, a main exchange, trunk lines connecting said main exchange with a plurality of groups of local substations connected by local lines, each substation having a set of push keys controlling said trunk and local lines and one of said stations of each group serving as an attendants station and being provided with a signal bell adapted to be rung from the main exchange, means for ringing up any one station of the group on the manipulation of a key at the attendants station, means operating at the attendants stationfor holding the trunk line, until the called station responds, automatic means operating to disconnect the trunk holding clrcuit whenever the attendant hangs up her receiver, and means for establishing talking communication between any two substations of different groups in the system by the manipulation of the trunk keys at said stations. v p

10. In an intercommun-icating telephone system, a main exchange,trunk lines connecting said main exchange with a plurality of groups of local substations each having a set of push keys, one station of each group beingan attendants'station, means operating on the manipulation of a key at the attend ants' station for ringing up any one station 'of a group, means for holding the trunk line until the called station responds, andfautomatic means for disconnecting the holding circuit whenever the 'attendants receiver is replaced on the hook.

11. An intercommunicating telephone system having a plurality of stations, a trunk at two or more of the stations for-establish ing a bridge across the trunk line to hold the latter whilecalling the desired station to answer a trunk call. I

12. The combination with an intercom? municating telephone system, ofa trunk line stem, and means f trunk line and for holding the trunk lineleading from the central 'ofiice exchange to said intercommunicating system and multipled with the several wstations thereof, and means at two or more of said stations additional to and in substitution of the telephone set thereof for establishing a bridge across the trunk line for maintaining the circuit continuity of said trunk line.

13. An intercommunicating telephone system having a' plurality of stations, a trunk line associated with the system, means at one of the stations for establishing a bridge across the trunk line to hold the latter While calling the desired station to answer a trunk call, and automatic means operating to disconnect the trunk holding circuit whenever the attendant at that station hangs up the receiver; whereby when the desired station is connected for conversation over the trunk line thedisconnect signal is under the control of the latter station.

14. In an intercommunicating telephone system, a main exchange, a trunk line connecting said main exchange with a plurality of local substations connected by local lines, each substation having a set; of push keys controlling said trunk and local lines, and each of said stations serving as an answering station over the trunk line, means at each of the stations for ringing up any other station of the intercommunicating system, means at each of the stations for holding the trunk line until the called station responds, and automatic means operating to disconnect the trunk holding circuit upon the hanging up of the telephone receiver at the station which initially answers over the trunk line.

15. In an intercominunicating telephone system, a main exchange, a trunk line connecting said main exchange with a plurality of local intercommunicat-ing substations each having a set of push keys, means operating on the manipulation of a key at any one of said stat-ions for ringing up any other of the local substations, means at each of the substations for answering on the while the call is being transferred to another st-ation', and automatic means for disconnecting-the holding circuit when the receiver at the station which initially answered the call isreplaced on the hook.

16. The combination with an intercommunicating telephone system, keys at each of said stations for connecting the telephone set thereof with thetrunk line, a. transfer key at each station for establishing a temporary bridge across the trunk line to maintain the central oflice signals unchanged, means at each of said stat-ions for establishing talking communication between that station and any otherstation of the system, whereby a call over the trunk line answered at one station may be transferred to another station, and automatic means operating to disconnect the trunk holding circuit when the receiver at the station which initially answered the call over the trunk line is recommunicating system and multipled to; two

or more stations'thereof, holding means for said trunk line at each of said stations independent of the telephone set thereof, switching apparatus for associating the holding means individual to a station with said trunk line, and means for rendering said holding means ineffective controlled by the station to which it is individual.

18. In an inter-communicating telephone system, the combination with a plurality of stations and conductors extendlng between said stations, of a. trunk line leading to said stations from a central exchange, a holding bridge associated with one of said stations adapted to be connected to said trunk line, and means for removing said holding bridge from said trunk line under the exclusive control of the associated station.

19. In an intercommnnicating tele hone system, the combination with a plurality of stations and conductors extending between said stations, of a trunk line leading to said stations from a central exchange, a holding bridge associated with one of said stations adapted to be connected to said trunk line, and means for removing said holding bridge from said trunk line under the control of the receiver hook switch at the associated station.

20. In an intercommunicating telephone system, the combination with a main exchange, of trunk lines connecting said main exchange with a plurality of groups of local substations connected by local lines, each substation having a set of push keys controlling said trunk and local lines, and 'one of said stations for each group serving as an attendants station and being provided with a signal bell adapted to be rung from the main exchange, means for ringing up any one station of the group on the manipulation of a. key atthe attendants station, an additional key at the attendants station for closing the trunk circuit and thus holding the trunk line until the called station responds, automatic means operating .to disconnect the trnnk holding cirquit whenever the attendant hangs up her receiver, and means .for establishing talking communication between any two substations of different groups in the system by the manipulation of a trunk keyat said stations,

21. In an intercommunicating telephone system, the combination with a plurality of stations, of conductors extending between said stations, means at each station for signaling a desired one of the remaining stations, means for establishing a talking condition between such twostations of the in tercommunicating system, a trunk line extendmg from an outside station to the stamunicating system and while the connection,

between such second station and the trunk line is being efiected, such holding bridge being released whenever the receiver at such first station is returned to the receiver hook thereat.

22. In an intercommunicating telephone system, the combination with a plurality of stations, of conductors extending between such stations, means at each stationfor signaling a desired. one of the remaining stations, means for establishing a talking condition between such two stations, a trunk line extending from an outside station to the stations of the intercommunicating system, signaling means at a first one of the intercommunieating stations adapted to be operated from the outside station, a holding bridge at such first station for holding the trunk line connection as desired during the calling and connecting to the trunk line of a second station of the intercommunicating system, such holding bridge being released whenever the receiver at such. first station is'returned to the receiver hook thereat.

change to such stations, signaling means at one of the stations adapted to be ope rated from such exchange and a holding bridge at such station for holding the trunk line connection as desired during the calling and connecting to the trunk line of a second station of the intercommunicating system, such holding bridge being released from such holding condition whenever the receiver at such first station is returned to the receiver hook thereat. 2 I

In witness whereof, I, hereunto subscribe my namethis ninth day of November A. 1).,

A JAMESL. MoQUARRIE. Witnesses:

' WILLIAM Me. A. SMITH,

EDWARD B. CRAFT. 

